In order to limit the number of elevators which are required to adequately service a building, elevator dispatching systems are designed to accommodate varying traffic patterns that exist in buildings. It has long been known to provide up-peak dispatching in the early hours of the business day, down-peak dispatching at the close of the business day, and off-peak dispatching during the remainder of the day. Up-peak dispatching takes into account the fact that many passengers will arrive at the lobby and simply desire to be transported to the floor of their work assignment. Similarly, down-peak dispatching takes into account the fact that many passengers simply want to be returned to the lobby on their way home. A variety of schemes are known for predicting the onset and termination of the need to provide up-peak service. Examples include U.S. Pat. Nos. 4,804,069, 4,838,384; and 5,035,302. In a commonly owned co-pending U.S. patent application of Kameli entitled "Prediction Correction for Elevator Traffic Shifts During Peak Conditions", Ser. No. 507/580,905 filed on Sep. 11, 1990, the peak period is adjusted in dependence on actual current conditions. An additional commonly owned co-pending U.S. patent application of Thangavelu entitled ""Artificial Intelligence" Based Learning System Predicting "Peak Period" Times for Elevator Dispatching", Ser. No. 07/644,356 filed on Jan. 22, 1991, utilizes historical data to improve determining the proper onset and termination of peak periods. A more recent innovation utilizes fuzzy logic to determine the onset and termination of peak periods, as set forth in a commonly owned co-pending U.S. patent application of Sirag et al entitled "Using Fuzzy Logic to Determine the Traffic Mode of an Elevator System", Ser. No. 07/879,558 filed on May 4, 1992. That system in turn utilizes the concepts set forth in another commonly owned co-pending U.S. patent application of Sirag entitled "Using Fuzzy Logic to Determine the Number of Passengers in an Elevator Car", Ser. No. 07/879,528 filed on May 4, 1992. In another commonly owned copending U.S. patent application of Sirag entitled "Estimating Number of People Waiting for an Elevator Car Based on Crisp and Fuzzy Values", Ser. No. 07/879,531 filed on May 4, 1992, there is disclosed a method of estimating the number of people behind an up hall call or a down hall call at a specific floor.
There are a variety of techniques which are utilized to assign hall calls to be answered by selected cars, some of which are disclosed in U.S. Pat. Nos. 4,363,381; 4,815,568; and 5,024,295. All of the aforementioned patents and applications are incorporated herein by reference.
It should be understood that the determination of when peak periods should begin and end is relatively independent of the manner in which an up-peak or down-peak mode of elevator traffic dispatching is carried out. That is, determining when to do it is relatively independent of determining how to do it. Typically, in prior elevator dispatching systems, if it is determined that the elevator dispatching mode should be an up-peak mode of dispatching, the system is usually shifted totally into the up-peak mode, reserving only one or two elevator cars (on a static basis) to service non up-peak traffic during the up-peak period.